Mr. Dan Wilton reports

FIRST MINING DELINEATES ENCOURAGING GOLD TARGETS AT THE BIRCH-UCHI GREENSTONE BELT PROJECT AND ANNOUNCES MANAGEMENT CHANGE

First Mining Gold Corp. has provided results from its 2023 drill program focused on the advancement of its Horseshoe and Atlantis drilling targets in the Birch-Uchi greenstone belt project (BUGB project) located in Northwestern Ontario, Canada. Winter drilling at the project comprised a total of 11 drill holes for 2,760 metres focused on three target areas: Saddle, Horseshoe and Atlantis.

First drilling by the company at the Horseshoe target included five drill holes totalling 1,589 metres which identified a significant gold mineralization system, with drill highlights including 0.48 gram per tonne Au over 48.5 metres in drill hole HOR23-001, 0.54 g/t Au over 57 metres in drill hole HOR23-002, and 0.64 g/t Au over 24 metres and 0.45 g/t Au over 14.5 metres in drill hole HOR23-003. The company also completed drilling at the Atlantis target which focused on EM plate modelled targets identified in the 2022 airborne geophysics campaign.

Assays for the Saddle target were previously reported and include gold intercepts of 0.92 g/t Au over 114.0 metres and 0.75 g/t Au over 58 metres (see news release dated July 6, 2023).

Project highlights

• Initial drill program tested multiple mineralization targets within the Horseshoe target area and successfully intersected mineralization over a 260 m strike length;
• Foundational data consolidation and integration with recent airborne geophysics into a preliminary 3-D model to further characterize, advance and identify exploration opportunities;
• BUGB project is proving to be prospective with three of four drilled targets identifying meaningful gold mineralization;
• Continued advancement and prioritization of exploration opportunities being delivered throughout the project area with opportunities for increased testing.

"Our exploration efforts continue to identify and advance new resource growth opportunities within our Birch-Uchi greenstone belt project, as demonstrated once again by significant intercepts of meaningful widths and gold grades in our latest results from Horseshoe," stated Dan Wilton, chief executive officer of First Mining. "The results from drilling at the Saddle, Horseshoe and Atlantis targets demonstrate robust gold endowment of this underexplored greenstone belt, all located within proximity of our Springpole gold project."

Horseshoe target

The Horseshoe target is located approximately 10 kilometres east-southeast of First Mining's Springpole gold project and is characterized by a significantly deformed and altered granodiorite intrusive unit that occurs in contact with a surrounding series of volcanic and sedimentary units of the Birch-Uchi greenstone belt. Mineralization is associated with increased sericite and silica alteration, moderate to intensely sheared granodiorite, higher concentrations of deformed quartz veining, and sulphides. The dominant sulphide mineralization is composed of pyrite and occurs as fine-grained to very fine-grained disseminations averaging 0.5 per cent to 4 per cent, with localized abundances up to 10 per cent. Veining is typically one centimetre to five cm in scale with higher densities corresponding to increased silica alteration. Mineralization is interpreted to be coincident with potential subparallel shear structures and increased sulphide mineralized areas.

The 2023 winter drilling campaign was focused on testing the preliminary 3-D geological model and to target sheared, mineralized granodiorite along the Swain deformation zone (SDZ) as well as its continuity down plunge. Modelling of the SDZ proximal to the target area incorporates a series of mapped splays that are interpreted to support a dilation zone of interest considered favourable for gold mineralization. Drill hole HOR23-001 was drilled to test the continuity of the mineralization between historical drilled holes, with holes HOR23-002 and HOR23-003 stepping east along the SDZ and testing the extension along strike in confirming continuity in the mineralization. The first three holes (HOR23-001, HOR23-002 and HOR23-003) all returned significant gold intercepts over a strike length of 260 m, with widths ranging from 14 to 48 m (see attached tables) which supports scaleability, and further opportunities for extension in previously untested areas.

Drill holes HOR23-004 and HOR23-005 are two stepout holes targeting an area that was highlighted by advanced geophysical modelling of the data from the company's 2022 airborne geophysics campaign. Hole HOR23-004 was targeting the lithological contact of a historically explored gabbro body known to host polymetallic Cu-Ni (copper-nickel) mineralization with increasing geochemical gold vectors toward a modelled contact. Drilling returned a down hole significant intercept that supports the presence of gold mineralization in the interpreted area, leading to opportunity for follow-up testing in additional exploration campaigns. Drill hole HOR23-005 targeted an extension of the SDZ dilation trend where coincident with geophysical interpretation of the modelled shear. The drill hole encountered breccia units providing structural insight to the target area, however, no significant gold values were encountered.

The Horseshoe target area has been a focus of recent geoscience compilation and target generation through First Mining's 2021 and 2022 exploration work programs. First Mining's exploration team completed data review, field site investigations consisting of mapping and sampling, airborne geophysics, and the application of 3-D modelling for a modernized geoscience approach to targeting. Through these work phases the company has identified an important exploration centre with expansion opportunities and substantial future resource potential.

Historical drilling was completed on the Horseshoe target area by previous operators, reportedly totalling 145 holes for approximately 24,000 m, with some being completed in the 1940s and more continuous exploration occurring between 1970 and 2000, which in addition to diamond drilling also included geophysics surveys, soil surveys, prospecting, mapping and trenching. Highlights from historical work programs include exploration focus of altered and deformed granodiorite which returned an interval of 16.5 m of 3.96 g/t Au in hole HSI84-008 (1984 -- St Joe Canada Inc.), as well as 15.0 m at 2.61 g/t Au in hole HI85-33 and three m at 10.97 g/t Au in hole HI85-36. Gold mineralization encountered in the historical drilling was hosted within highly silicified zones of increased quartz veining and strongly altered granodiorite consistent with the expansions and logging descriptions of First Mining. In combination with the 2023 drilling, results are indicative of a mineralization envelope that is host to significant gold potential and which will form an important focus for additional follow-up exploration.

Atlantis target

Additional exploration of the BUGB project during the winter program included an initial drill hole testing the Atlantis target within the Birch property, located approximately four km north of First Mining's Springpole gold project, where several significant high-grade gold settings have been identified in previous exploration campaigns. Historical exploration includes the discovery of centres of high-grade gold in quartz veining that is hosted within intermediate volcanics, mafic volcanics and banded iron formation lithologies. Mineralization across the property has returned gold grades of up to 15.3 g/t Au in rock grab samples at the Canamer target (see news release Jan. 17, 2023), toward the southeast of Atlantis during the 2022 field campaign, and historical drilling programs on the HGI target, located toward the east-southeast of Atlantis, reported grades of up to 113.94 g/t Au over 2.95 m (hole TWBL-096) and 246 g/t Au over one m (hole P255A-078).

Recent airborne geophysical surveys coupled with continuing data compilation throughout 2021 and 2022 have evolved a new series of underexplored targets for drill testing and groundwork follow-up. The Atlantis target occurs as a series of plate modelled EM conductors identified in the 2022 SkyTEM geophysical campaign, coincident with a magnetic high trend interpreted to be folded iron formation stratigraphy.

This target was tested with one drill hole during the recent program in an effort to discover new gold mineralization in analogous structural and stratigraphic settings to other known mineralized occurrences on the property. Drill hole BIR23-001 was a technical success in that it intercepted significant quartz veining, as well as multiple zones of pyrite and pyrrhotite sulphidized iron formation stratigraphy that will provide additional vectoring within the target and propertywide area. Gold grades returned were below detection limits, with additional characterization work and target vectoring in this target area still to be completed.

First Mining's exploration team is continuing to analyze data from the 2023 winter drilling campaign around the Horseshoe and Atlantis targets, from which the learnings will further be incorporated into a revised and updated geological model to support continued exploration opportunities.

"Our dedicated exploration and support teams are making tremendous progress at the Birch-Uchi project as we are continuing to push forward with mapping and sampling on a multitude of prospective areas which will uplift our database strength and support improved modelling and informed geological targeting in the district surrounding Springpole," stated James Maxwell, vice-president of exploration for First Mining.

Birch-Uchi greenstone belt project

First Mining's BUGB project hosts significant district-scale exploration leverage in forming part of a consolidated over-70,000-hectare mineral tenure. The property and broader greenstone belt host historic production centres that demonstrate a strong gold endowment and an affinity for potential new discovery. First Mining's extensive BUGB property position is located within the Red Lake mining district and is situated approximately 80 km east of the Red Lake mines complex of Evolution Mining, and 75 km northeast of Kinross Gold's Dixie project (formerly owned by Great Bear Resources Ltd.). Geology of the region comprises Archean greenstone terranes that are endowed by significant gold mineralization inclusive of orogenic and alkaline intrusion-related deposit styles. Initial data compilation and validation to date has indicated that the region demonstrates an underexplored and previously fragmented exploration immaturity that is well levered to the company's strategy of consolidation and district screening.

The Birch-Uchi greenstone belt hosts multiple gold mineralization styles throughout, which supports having a strong multidiscipline geoscience foundation that can be applied in an integrated and iterative targeting approach. Early targeting and vectoring elements highlight consolidated target opportunities surrounding the Springpole gold project.

Analytical laboratory and quality assurance/quality control procedures

All sampling completed by First Mining within its exploration programs is subject to a company standard of internal quality control and quality assurance (QA/QC) programs which include the insertion of certified reference materials, blank materials and a level of duplicate analysis. Core samples from the 2023 drilling program were sent to AGAT Laboratories in Thunder Bay and Mississauga, Ont., where they were processed for gold analysis by 50-gram fire assay with an atomic absorption finish, and multielement analysis (including silver) by inductively coupled plasma (ICP) method with a four-acid digest. AGAT Laboratories systems conform to requirements of International Organization for Standardization/International Electrotechnical Commission Standard 17025 guidelines and meet assay requirements outlined for National Instrument 43-101 Standards of Disclosure for Mineral Projects.

Senior management change

Samir Patel, the company's general counsel and corporate secretary, will be leaving his role at First Mining, effective July 21, 2023, having notified the company that he will be pursuing another opportunity in the mining industry. Following Mr. Patel's departure from the company, Lisa Peterson, the company's chief financial officer, will assume corporate secretary duties on an interim basis.

"We would like to thank Samir for his service and dedication to First Mining. As one of the company's longest standing employees, Samir has been a key part of the development of First Mining, and we wish him well in his future endeavours," stated Dan Wilton, chief executive officer of First Mining.

Qualified person

Hazel Mullin, PGeo, director, data management and technical services of First Mining, is a qualified person for the purposes of NI 43-101, and she has reviewed and approved the scientific and technical disclosure contained in this news release.

About First Mining Gold Corp.

First Mining is a gold developer advancing two of the largest gold projects in Canada, the Springpole gold project in Northwestern Ontario, where it has commenced a feasibility study and permitting activities are continuing with a draft environmental impact statement (EIS) for the project published in June, 2022, and the Duparquet, Pitt Gold, Duquesne and Porcupine East gold project in Quebec, a collection of advanced-stage development assets located on the Destor-Porcupine fault zone in the prolific Abitibi region. First Mining also owns the Cameron gold project in Ontario and a portfolio of gold project interests including the Pickle Crow gold project (being advanced in partnership with Auteco Minerals Ltd.), the Hope Brook gold project (being advanced in partnership with Big Ridge Gold Corp.), and a large equity interest in Treasury Metals Inc.

First Mining was established in 2015 by Keith Neumeyer, founding president and CEO of First Majestic Silver.

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